It is conventionally known that a fuel vapor processing device is capable of recovering fuel vapor from a fuel tank, and supplying the recovered fuel vapor to an intake system of an internal combustion engine. The fuel vapor processing device of this type has a diagnosis function for diagnosing a leak from a fuel vapor processing system. For example, a fuel vapor processing device described in JP 2014-126006 A includes a sealing valve that seals a fuel tank from the atmosphere, a canister that recovers fuel vapor, a canister internal pressure sensor, a tank internal pressure sensor, and others. The fuel vapor processing device is configured to perform a leakage diagnosis for a fuel vapor processing system based on detection values of the canister internal pressure sensor and the tank internal pressure sensor, and perform a diagnosis for the sealing valve.
The fuel vapor processing device described in JP 2014-126006 A has separate sensors for the fuel tank internal pressure detection and the canister internal pressure detection to determine the presence or absence of a fuel vapor leak from the fuel tank and the presence or absence of a fuel vapor leak from the canister. Accordingly, the fuel vapor processing device uses two pressure sensors in total. This configuration requires a sufficient number of harnesses for the pressure sensors to cause electrical continuity between an electronic control unit (ECU) and the respective pressure sensors. In this case, a problem of a complicated device configuration may arise.